Eliminating effects of variations in current supplied to audions



July 18, 1933.

G. a. cRousE 1,918,899 ELIMINATING EFFECTS OF VARIATIONS IN CURRENT SUPPLIED TO AUDIONS Filed Dec. 27, 1926 3 Sheets-Sheet l l l l l l l 2E "Pl/2f E Pofenf/a/ July 18, 1933. B CROUSE 1,918,899

ELIMINATING EFFECTS OF VARIATIONS IN CURRENT SUPPLIED TO AUDIONS Filed Dec. 27, 1926 3 Sheets-Sheet 2 July 18, 1933. B CROUSE 1,918,899

ELIMINATING EFFECTS OF VARIATIONS IN CURRENT SUPPLIED TO AUDIONS Filed Dec. 27, 1926 3 Sheets-Sheet 3 Aud/o Amp f)?!- gwuento 61cm war.

Patented July 18, 1933 ETELE? S EATES GEORGE B. CROUSE, OF VIOODCLIFF, NEW JERSEY, ILSSIGNOR, BY MESNE ASSIGNMENT-S,

TO BYRNES, TOVJN? 'ID 8c 1 32 CHARLES H. POTTER, JAD'IES 3, OF WASHING-TOTE, D. CL, A FIRM CONSISTING OF PIERCE, AND RICHARD L. SCHEFFLER ELIMINA'IING sensors or VELRIA'LIONS 1H CURRENT SUPPLIED TO AubmN's' Application filed December 2 This application is a continuation in part of my co-pending application Ser. Noifillifif 558, filed August 22, 192%, Eliminating eifects of variations in currents supplied to audions, and relates to methods of and apparatus for eliminating in the output circuit of an audion the effects of variations in current supplied to one or more of its elements.

Recognizing the desirability and advan tages of being able to supply the audions of a radio receiver directly from lighting circuits without the use of batteries, many in ventors have obtained patents for arrangements intended to accomplish this purpose, but for one reason or another none of the patented arrangements with which I am familiar provides a current supply which is absolutely free from all alternating current components or short period. variations, such as is required for thesatis'factory operation of audious, particularly when used asrle; teeters and as amplifiers in radio receivers it is thereliore the usual practice to supply the current "for the audiions'of radio receivers from primary or secondary batteries, but their disadvantages are many and well known, particularly to those who have had occasion to use them.

Vhcn using rectified and filtered alternating current on the filaments or plates in audio-ampliliers it'is frequently found that a perfection of filtering sutiicient for quiet opera"on with one stage'w'ill' not be suitable when ?-..'al are cascade-" This, of course, due to the fact thatthe ripple occurring: in the first aud'ion,"(in a radio receiver; the detector tube) while inaudible in the output of that tube, will be amplified through eucccediu stages to cause an obj-e tienable disturbance. In aecorrlancc'w'ith this inventionthe disturbauce which arises in the output circuit and due to the energizing of an element of th audion from a source a directcun rent havingalteruat" 'compo'neuts reduced elf nated by impressing upon an- I er e-le t ol the audiona ripple voltage which is derived fronrthe 'sarne source ofeuare and is o adjusted to magnitude and phase that its cllect on the output circuit 1926, {Serial N0. 15?,311.

cmiuteracts the disturbing effect of the cur-- rent applied to the first element.

5 The invention may be practiced invitwo general ways. The direct current having, alternating components may be used to "ener-z ice both the filament and the plate circuits of the audion, and the efi'ects in the output circuit of the alternating componentssrnay be eliminated by a suitable adjustment of the magnitude and phase of the alternating1components impressed upon the separate elemerits. irlternatively, the source off-direct current having alternatingcomponents iriay be employed to energize but one elenient e fi the audion and the disturbing elfeetsfliereef may he counteracted by impressing regimenother element a ripplevoltage deri-vedlfircm the same source and suitably djusted a to phaseandmagnitude. 1

With either general method, sever eilie methods are available for carrying" out the invention. A disturbance in' the output circuit due to variations in-the'cu plied to the filament may be v v the application to the'grid to the late of an alternating: voltage of proper-pile d magnitude, When the disturb'aricf arises from the application to the plate cirquit'of a current having alternating conrpunentsj tlfe et cts thereof ruavbe opposed ea on to the grid or to the lilament of alternating" volt-age ofproper phase andiiii nitude. When both the-plate and filamnt are energized from a common source, Jenergizir z circuits maybe so designed that the effects in the output circuit of theffripifle voltages applied to the separate elements-W1 counteract each other. An object of the invention isto pr'o a method of and apparatus fOfl'GdtlCll'lg; n or eliminating from the output circuit ojfan audion. eii'ects of residual ripple in the fcu 'rrent supplied to the filamentand/or plate. An object is to provide a. method of ahd a'p para .7 for energizing an element of an au-' die-n from a source of direct currentihaving a ltern ating components, in which a counter electromotix-e Force of proper magnitude and phase is app d to one of the other'el'mti lfi of the audion; the counter electromotive force being taken from the source which tends to create the disturbance, and being automaticah ly maintained in proper value both as to phase and magnitude. A further object is to provide methods of and apparatus for eliminating the effects in the output circuit of an alternating component in the current suppiied to the filament. More specifically, an obje'ctis to provide methods and apparatus in accordance with the object last stated, in which the disturbing cilects are eliminated by impressing upon the plate circuit an alternating voltage to produce in that circuit a ripple effect opposing that due to the presence of alternating components in the filament current. i

The particular nature of the invention will appear most-clearly from a description of certain preferred embodiments and their applications to radio receivers as shown in the accompanying drawings in which:

Fig. l is an electrical diagram of an audion circuit in which the filament and plate are energized from the same source;

Fig. 2' shows the potential characteristics of the current supplied to the circuits of F ig. 1;

Fig. 3 is an electrical diagram similar to that of: Fig. 1, but with additional elements in accordance with one embodiment of the invention;

at is a similar diagram in accordance with another embodiment of the invention;

Fig. 5 is a similar diagram in accordance with a third embodiment of the invent-ion;

- Figs. 6 and 7 are electrical diagrams of andion-circuits in which only the filament is energized from the source having alternating components;

' FigsBA and 8B arevector diagrams illustrating the relationship of the alternating voltages established in the circuit of Fig. 7; v9 is anelectrical diagrain of an audion circuit in which both the filament and plate are, supplied with rectified and filtered current-from a common source, but only the plate circuit filter is effective'to remove all alternating components;

. Fig. lOis a diagram of an audion circuit in which only the plate circuit is energized from a source having alternating components, and v Fig. 11 is a vector diagram illustrating the relation of the voltages established in the circuit of Fig. 10.

For convenience the general principles of the invention will be explained in connection with the simplified diagrams of one or more audion stages as the various applications of the invention to radio receivers will be ap parent. therefrom.

F or the purpose of illustrating a current supply containing ripples or short period variations there is shown inFig. 1 a battery 1 of suitable voltage for operating the plate circuit of an audion and in series with this source of direct current there is an aiternaiing current generator The potential sup plied at the terminals 3 and 4 will the: h are the characteristics shown in Fig. '2, consisting of a direct current component represented by the straight broken line A and an alternating current component represented by the solid wavy line B. The present mvention contemplates the elimination from the output circuit of the ripple cliect which would he produced it this alternating component B were impressed upon the known forms of audion circuits.

The audion is shown as connirising the usual three-element vacuum tube having a filament 5, a grid 6 and plate 7. The filament is connected to the source terminals 3, 4 through a resistance 8 of such. magnitude as to reduce the potential across the filament to a suitable value. The secondary winding 9 of a suitable input transformer having a primary 9a is connected in the usual Way with one end to the grid 6 and the other end to, say, the positive end of the filament The plate 7 is connected to the positive terminal 3 through a device which is shown as a telephone receiver, but it may be the primary of a repeater for connecting the output circuit to a second audion.

Since the potential applied to the terminals 3 and 4 has an alternating current component (B, Fig. 2). the current passing through the filament will also have an alternating current component, which will be in phase with the potential, since the filament circuit is en tirely resistive. The alternating potential across the filament itself, which will only be a small fraction of that across the terminals 3 and 4 since a large part of it is dissipated across the resistance 8 will cause a voltage to be applied to the grid in phase with the drop, since the grid is connected to one end of the filament. A variation of the plate current of the audion will therefore occur, which will be an exact reproduction (neglecting the small distortion effects of the audion) of the alternating potential across the filament, but will be 180 out of phase With it. The alternating potential at the terminals 3 and 4 is applied directly to the plate circuit and will cause a variation in the plate current which is in phase with the potential, except for the phase shift caused by the inductive device 10. 1

The effect of the filament variations on the platecurrent due to the action of the grid will generally be smaller than the direct effect of the variations applied to'the plate. 5 s may be seen by applying some usual values to the quantities. Let

Ef=filament voltage drop, D. C.=5 volts. Rf=filament resistance= ohms.

i Ep plate voltage, D. C.= volts.

X20 plate impedance=20,000 ohms.

Xc impedance of device 10, at frequency of ripple=20,000 ohms.

=amplifying constant of audion=9.

R8 resistance of 8 380 ohms.

Eb=value of alternating current potential at terminals 3 and i=1 volt.

The alternating current potential across the filament, Ebfiwill be given by the formula Rf Eb (Rf RS Since approximately only half of this potential is effectively appliedto the grid, the effect on the output or plate circuit is equivalent to a voltage on the plate of (see Van der Bihl. Thermionic vacuum tubes, page 150 et seq.)

By substituting the numerical values given above in this equation, there is obtained a value of the plate'voltage fluctuation due to the filament of'0225 volts, Whereas, as stated previously, analternating potential of 1 volt is applied directly to the plate, but in opposite phase to the filament effect.

In order that there shall be no alternating current component in the output, the alternating potential applied directly to the plate must be made equal to the plate voltage variations due to the filament effect, that'is. to 0.225 volts for the electrical constants given above. 1

This may be done in several ways. One means of conveniently accomplishing it is shown in Fig. 3 which is similar to Fig. 1 (as far as elements 1 to 10 inclusive are concerned), but an inductance 11 a capacity 12 and: a resistance 13 are added to the plate circuit. The relative values of the capacity and inductance are such as to make the combination anti-resonant at the frequency of the alternating component of the supply. This combination, if properly designed as to internal losses, will reduce the alternating component of the plate supply to a value considerably below the value of the plate voltage fluctuations due to the filament effect without shifting its phase. The value can then be. increased by the resistance 13 to that necessary togivezero alternating current in the output of the tube. When thisadjustment is properly made, thenplate circuit of the audion has an effective impedance of infinity for the frequency of the supply ripple, and therefore there isno phase shift etl'ectdue to the inductivedcvice 10. Since.

in practice, the. frequency of the supply ripple is usually low, the condenser 12 serves as a by-pass for the higher useful signal frequencies and prevents intercoupling at these frequencies. I V

Another'arrangement by which the invention may lee-practiced is'shown in Fig. 4, in

ment effect. instead of, as in the case of Fig. 3,

reducing the plate effect. In order that there shall be no phase shift between the filament and plate effects, this capacity by-pass circuit is made resonant at the frequency of the supply ripple, by means of the inductance 16. The amount of current by-passed is adjusted by means ofthe resistance 15.

Still another way is: which the invention may be practiced is shown in Fig. 5, in whichagain the parts identical with those of Fig. 1 are similarly numbered. In this arrangement the filament effect is increased sufficiently to cancel the plate effect of the supply ripple by applying to the grid an additional alternating potential, by means of the coil 17 placed in series with the filament lead and in ductively related to the input coil 9 in the grid circuit. The bracket in this figure indicates that the primary coil 90 of the transformer is also inductively related to the sec ondary coil 9.

The above explanation in connection with F gs. 3. 4 and 5 shows three Ways in which the invention may be practiced, in the first of which the balance is obtained by reducing the plate circuit ripple; in the second, by in creasing the alternating potential drop across the filament; and in the third, by increasing the filament effect by means of the grid. It should be understood that in the numerical example given and in the embodiments shown, values have been taken for the quantities. which are usual for small tubes. In the case of tubes having a high amplification constant, or having a high filament resistance, and a low value direct current plate poten tial, that the filament effect will normally be greater than the plate effect. modifications of the arrangements -shown will readily suggest themselves to those skilled in the art to which the invention relates.

The circuits as above described illustrate the general method of practicing the invention when energizing both the filament and the plate from the same source by an adjustment of the ripple effects due to alternating components supplied to the separate elements. The invention may be practiced in an analogous manner when alternating components are present in the source supplying only one of these elements by impressing upon the other element a suitable ripple voltage which derived from the same source.

Fig. 6 is a circuit diagram illustrating an audion detector feeding into an audio amplifier, the filaments being energized by rectified alternating current and the plates being energized by substantially pure direct current. The input circuit of the detector includes the 1 audio transformer T and a suitable portion of thelate battery 21.

'The laments of the detector and amplifier areenergized from a source of alternating current 22 through rectifier 23 and filter 24. The filter 24-is of such design and construction that the output current has alternating components of sufiicient magnitude to produce ripple eliects in the output circuit of a detector tube. To reduce or eliminate these effects; compensating rbltage is applied to the grid by atran's"former whose primary 25 is connected directly across the filament and whose secondary 26 is in series in the grid circuit.- To reducetlre loss of direct current, the

1 primary winding '25 h as a relatively high resistance, aiid to allow afree path for radio frequency currents a small condenser 27 is shunted across the-secondary; The transfornier is so constructed andfarranged that its output voltage'is' equal to the effective alternating voltage-in the grid circuit due to the filament ripple, and is of opposite phase.

The coi'upensating ripple voltage may be impressed upon the plate by a circuit such as shown in Fig.7. The general construction of the'deteotor and amplifier circuits may be substantially identical. with that shown in Fig. (rand; corresponding elements in the two views areftherefoi'e 1 identified by the same numerals." Inthe circuit of F 7 the'lower side of the inputcircuit is'connec'te d to the filament and a: resistance 28 across which the compensating potential is impressed is made a series elementof the plate-'circuit.

The filament current is derived from ascurceofaltern ating current through a transformerhaving two secondary windings 29 across'which the two rectifier-s 29' are connected in-theu'sua'l manner: Thefilter sys tem wh ch is shown for illustrative purposes isof the type described inmy copending application SGT. No. 130252. filed August 19, 1926. The filter includes a choke coil 30 in series in the 'pbsitiv'e sideof the line, and following the cholre a-pair cf resistancesgl' and in series across th-eiine. The primary33 of an auto transformer is connectcdfacross the'rcsistance 31and the secondary 34 is connectedthrough'a second series choke 3'5 and through'the filaments tothenegative side of theline. To apply'the compensating voltage to theflplatecircuih'a connection is made from the'plaite 'endo'f resistance 28to a point on the cross resistancc- 313 2 through a condenser 37. K

The manner'in-which the circuit of Fig. 7 corrects-forth-e residual ripple in the filament circuit may; be best understood by refer' of ripple in the filament. \Vhen this vector is positive, the grid is positive. Then the voltage existing across the space between filament and grid will be in phase with I and may be: represented by E,. There is a further drop in this circuit occasioned by the complex impedance of the grid leak 18 and condenser 19; The current through thiscomplex impedance will. divide, the part I through the resistance, lagging the part I through the condenser. The voltage will be in phase with L, as shown at E Then the vector sum of E 21ILClE represents-theeffective value of the ripple voltage applied in the grid circuit; This voltage -E is. approximately one-half the value of the alternating current drop across the total filament i'il Now the voltage E "applied to the grid causes a voltage E where zisthe voltage amplification constant of. the tube) and of identical phase with IE (since a more'positive grid means an increase of plate. current). This voltage in the plate circuit is represented by E in Fig. 8B, which diagram-is made on a reduced scale to bring the diagram-within the limits of the sheet. Returning tothe first diagram, the voltage E has'its source in the voltage across the filter resistance 32, and since between the filament and. the resistance 32 there is alarge inductive reactance (coils 34 and 35) the drop across resistance 32 may be represented by a very-along vector, whose direction will be almost at right angles to E and whose length will be beyond the limits of the diagram,- as shown by the lineE This voltage E5 is represented in direction again in the second diagram.- y I Now the, problemirequires that a compen sating voltage E equal and opposite toithe ripple voltageE shall be setup in the plate circuiti'which compensating voltage must be derived from E A close approximation to the solution ;-will ibei obtainedby, theuse of a high condensive reactance,. as condenser 37;, which will cause a voltage dropv approxi mately at right angles to E as E the mag nitude of whiclrma-v be adjusted'by the slider on-the resistance' 32. The compensation ob tained by the arrangement shown will ordinarilv'be close enough for practical purposes, but if closer results are desired, it'isonly necessaryto substitute acomplerr'impedancc of proper characteristics for the resistance 28, as Willhe readily .under stpod byofne skilled inthea rt. Y

FAlthough the apparatus shown in Fig.7. will compensate for only a "single frequency; it has becnfound that with the type-offilters suitable for supplying the filaments ofaudions, only one frequencyin-the output is of suiiicient magnitude to require any special means of suppression. It will also beappar entfrom the vector diagrams-that any desired degree of compensation .may be efi'ected.

by a proper selection of the constants and character of the compensating impedances'.

It may be desirable insome cases to replace the condensive reactance 37 by inductivc or resistive reactance, or combinations of any or all of them. By constructing a scale diagrai'n' of the character above, for the particular constants: oi the filter and udion connections, one may dctcri n-e thecharacter and value of impedani o y 'euiployedl hen a rectifier am, Hui?!" am; used to supply'the plate'ct'lrrent for audio!) tubes, the potentiometer ordinarily useel'to take otiinterm'ediatc direct=current voltages may be used to replace the resistance 32, as shown in Fig. 9. In this figure, the several elements of the detector and amplifier circuits which are identical with corresponding elementsof Figs. 6 and 7 are identified by the same numerals. The filter for the rectified cur rent supplied to the filaments is of a well known type comprising the series inductances 40', 41, between which a resistance 4-2 is connected across the line. As before, it is assumed that the residual. ripple passed by this filter will cause a disturbance in the detector tube output circuit but will be without substantial effect in the amplifier stages.

= The plate supply is illustrated as a combined rectifier and filter of the type shown my'copending"application Ser. No. 130,- 252. A primary 43' of atransforiner having a core 44 is connected across the alternating current source','and the terminals'of the secondzi'ry'Winding4-5 are connected to the comnion'neg'a'tive wire 46 and tliro-ugha rectifier 47 to the positive output wire 48, respectively." The-filter comprises the condense-rs 49, 5t)" and51, the mutual reactance coil 52' and the'choke coil53. Since it' usually nccessary to supply a number of different direct current voltages for thedi-fierent audions usediin a radio receiver or amplifier, a potentiometer 54 is connected across the output The plate potential. of the detector audion is taken off of this potentiometer at the points 4 A d nates- 56 is connected between a point on'the l'resistance 42 of the filament current filter andfa point on the potentiometer It will befse'e-n that this condenser is the equivalentofthe condenser 37 of'Fig. 7 and. that that portion {of the potentiometer betweenthe pointof connection of this condenser and the negative wire lfi is equivalent was resistance 36 of Fig. '5. 1 Vector dia grams similar to Figs.'8A, 83, may be constructed to fit the'circuit conditions of Fig. Qf'fAithough the plate current is taken from-an alternating current sou-rce,'itis assl-lniedtliat the output from the plate current filter is substantially free f'romalternating components. 7

In Fig; 10 have illustrate-d an arrangement forcorrecti-ng foralternating compo nents in the plate supply. As is indicated by the same referencenumerals as in Fig. 9, the general construction of the radio and audio circuits, and of the plate current supply may be substantially the same as in Fig. 9. In

the circuit of Fig. 10', however, the detector filament is energized from a battery 60 and! the compensating ripple voltage is intro duceol into the grid circuit th-rouglr the fila V V ment. The secondary 61 of a transformer having an iron core 62 is introduced intothe filament circuit, the primary ofthis'transe former, 63, is connected across the output of the filter (i. e. across the terminals of the Potentiometer A resistance 64 is included respectively the currents through the grid leak 11 and condenser 12, and the vollfag'eE, is the drop across this complex impedance. The vector combination of Ei and E gives, as before, one-half the total alternating cm"- rcnt voltage across the filament, represented by E To eliec't perfect compensation, there must be present in the plate circuit a voltage 1E; and of opposite phase to E This voltage is shown as E and is directly derived from the drop across the resistance 54'. The analysis need not be carried fin rther to show that approximate compensation may be tained' by applying the voltage drop'aer'oss 54 which is in phase with E 'to the filament circuit, via the transfor-mer 61-6263, and

that if exact compensation is desired, itniay be obtained by the use of a 'comp'l'ex inn ped ance in place of the resistance 642 For the purpose of illustration, I-ha'v'e" shown circuits in which the compensating voltage was applied in a single amplifying stage, but it will be apparent that the 'inven tion may be practiced in other ways. When the alternating components are coiirrparatively Weak, a correction applied at the d'e tector tube may be sufficient to eliminate all objectionable efi'ects of the ripple. When the residual ripple components are stronger, compensation may be necessary in other stages of the amplifier and similarly, when the ripple is exceedingly weak, a compensation applied in one of the audio stages may adequate. The radio and audio circuitsof the receiver or amplifier form no part'of the invention and may take any suitable form. I claim: I. In the energization of a plurality of the circuits of an audion from a source of direct current containing periodic alternating components of audible frequency, the method of suppressing the effects of such alternating components which comprises energizing one of said circuits with direct current from said source and containing such alternating components in the ratio in which they are pres ent in said source, and energizing another of said audion circuits with direct current from said source and containing alternating components in a ratio different from that in which said components are present in said source.

2. In the energization of a plurality of the circuits of an audion from a source of direct current containing periodic alternatingcomponents of audible frequency, the method of suppressing the effects of such alternating components which comprises employing in said circuitsdirect current from said source to establish the required direct current potentials upon the respective audion elements included therein and varying the relatiy e magnitudes of the direct and alternating potentials which said source impresses upon one of said elements to thereby maintain said element at the required direct current potential while impressing thereon an alternating potential to suppress the effects of the alternating components.

3. The method of operating an audion having a cathode, a plate and a grid, which com prises applying to two of said elements from a common source of direct current containing alternating components two potentials of such .relativeyaluesas to establish on said elements the direct current potentials required for operation of said audion, and independently of said established direct current potentials adjusting the relative magnitudes of the alternating potentials established .on said elements by said source to thereby render their combined effects upon the output circuit substantially zero.

4. The method of operating an audion from; a source of direct current containing alternating components of audible frequency, which comprises energizing one of the circuits of said audion from said source to es-. tablish in said circuit the direct current potential required for operatioi'iof said audion, and independently of the relative direct current potentials thereby established on the audion elements by said source impressing upon another circuit of the audion an alternating voltage effective to suppress the effects in the output circuit of alternating componentsincidentally present in said first circuit.

5. In the operation of an audion amplifier stage having an input circuit, an output circuit and a cathode-heating circuit, the cathode-heating circuit being energized and the direct current grid. bias being derived from a source of direct current having alternating components of audible frequency, the method which comprises impressing upon one of the other circuits an alternating voltage of a phase and magnitude to counteract in the plate circuit the effects of the alternating components in the cathode-energizing cur rent.

6. The method as set forth in claim 5, wherein said alternating voltage is applied to the plate circuit.

7. In the operation of an audion amplifier stage having an input circuit, a plate circuit and a cathode heating circuit, the cathode heating circuit being energized and the grid bias being derived from a source of direct cu rent having alternating components of audible frequency, the method which comprises energizing said plate circuit from a source of substantially pure direct current, and superposing upon said plate-energizing current an alternating voltage of a phase and magnitude to counteract in the plate circuit the efiects of the alternating components in the cathodeheating current.

8. In the operation of a plurality of cascaded audion stages, the method which comprises determining the direct current potential ofan element of each of the audions with reference to another element of the respective audions by a common source of direct current containing periodic alternating components of audible frequency, and suppressing the effects of such alternating components in the output circuit of said cascaded stages by reactively coupling said source to but one circuit of only one of said stages, an alternating voltage derived from said source and of a phase and magnitude effective to eliminate disturbing ripple effects from the output of said cascaded stages.

9. In the operation of cascaded sta es comprising an audion detector and an an io amplifier from a source of direct current having alternating components of audible frequency, the method of eliminating the effects of said components of the energizing current which comprises compensating for said effects in only the detector stage by supplying to a circuit thereof an alternating current additional to said energizing current.

10. In the operation of cascaded audion detector and amplifier stages, the method which comprises energizing the cathodeheating circuits of said stages from a source of direct current having alternating components of audible frequency, and impressing upon another circuit of said detector stage an alternating voltage counteracting the effect in the output circuit of said cascaded stages of the alternating components in the cathode-heating circuits.

11. The method as set forth in claim 10, wherein said alternating voltage is impressed upon the plate circuit of the detector stage.

12. In apparatus for energizing an audion having a grid circuit, a cathode-heating circuit and a plate circuit, the combination with means for energizing one of said circuits from a source of direct current having alternating components of audible frequency, of means operable independent of the direct current potentials impressed upon said circuits for establishing in another circuit of said audion an alternating current of phase and magnitude counteracting in the plate circuit the effects of the alternating components in the said source.

13. The combination with apparatus for energizing one circuit of an audion amplifier stage from a source of substantially pure direct current, and another circuit thereof from a source of direct current having alternating components of audible frequency, of means for establishing in said first circuit an alter nating current free from all direct current components and derived from said second source to counteract the eficct in the space current circuit of the stage of the alternating components in current supplied to said second circuit.

14. Apparatus for energizing an audion, comprising a filament current supply derived from a source of direct current having alternating components, and reactive means for impressing upon the plate an alternating voltage derived from said source and free from direct current components, the impedance of said means being such that the phase and magnitude of the applied voltage pro- LJi duces a neutralization in the plate circuit of the effects of the alternating components of the filament supply.

15. In apparatus for energizing an audion, a source for supplying to the filament circuit direct current containing alternating components, a plate circuit including a current supply connected between said filament and the audion plate, an impedance across which said filament source establishes an alternating voltage, and circuit elements for connecting said impedance to the plate circuit of said audion to impress therein an alternating voltage free from direct current components for counteracting the effects in said plate circuit of alternating components in said filament circuit.

16. The combination with apparatus for energizing circuits of a plurality of cascaded audion amplifier stages from a source of direct current having alternating components, of means for impressing upon a circuit of one of said stages an alternating voltage derived from said source, free from direct current components and of a phase and magnitude to neutralize the effect in the output circuit of the cascaded stages of the alternating components of said source current.

17. In apparatus for energizing an audion from a source of direct current containing periodic alternating components of audible frequency, the combination with meansdefining directcurrent paths for impressing upon the respective audion elements from said source the. direct current potentials required for operation of the audion, of alternating current impedance in one 'of said paths for altering the ratio of the aiternating to direct components in the current supplied by the said path to said audion to render negligible the effect of alternating components the current supplied through the other direct current paths.

18. In a network of an audion stage, the combination with a plurality of sources of direct current incorporated in said network to determine the relative direct current potentials of the grid, cathode and anode of the audion, one of said sources containing periodic alternating components of audible frequency, of a corrective alternating current impedance coupling said last mentioned source with a circuit not energized thereby with direct current to impress thereon an alternating voltage tree from a direct current component.

1.9. In a system of cascaded audion amplifier stages including a detector and an audio amplifier, the combination with a source of direct current containing periodic alternating components of audible frequency, connected to the filament circuits of the audions for heating the same, and a source of direct currentfor energizing the plate circuits of said audions, of an impedance path conductive for alternating current and non-conductive for direct current connected between the circuits associated with said two sources of direct current for impressing upon said plate circuits an alternating voltage to suppress the effects of alternating components in said filament circuit supply.

20. In apparatus for'energizing a plurality of the circuits of an audion from a common source of direct current containing periodic alternating components of audible frequency, the combination with circuit elements connecting said plurality of circuits to said source to establish in said circuits, the respective direct current potentials required for operation of said audion, and means for adjusting the magnitude of the alternating potential established in one of said circuits by said source to such value that the effect upon the output circuit of such alternating components is substantially zero.

21. In the network of an audion stage, a cathode circuit, a plate circuit, separate sources of direct current for energizing said plate and cathode circuits, a grid circuit ter minating on such point in said cathode circuit that the direct current bias required for operation of the audion is obtained by the potential drop in said cathode circuit, one of said direct current sources containing perito' pass filtered direct current thereto, of means for impressing upon another circuit of said audion a neutralizing alternating voltage derived from said'source, said neutralizing voltage being substantially free from (lirect current components and of a phase and magnitude to substantially suppress the effects of alternating current components passed to said first circuit by said filter net- Work.

GEORGE B. CROUSE. 

